Quick disconnect type couplers and safety valves are old in the art, there having existing needs for means of connecting tools utilizing compressed air with the compressed air source, especially where flexible hose coupling between the compressed air source and the air tool is necessary. The present couplers available suffer from shortcomings such that when the male plug is disengaged from the coupler, the compressed air held in the air tool and in the flexible hose leading from the plug to the air tool causes the plug to shoot out of the coupler and thus be potentially harmful. Further, the present couplers fail to hold the male plug when force is exerted upon the plug pulling it out of its connection with the coupler. Similarly, safety check valves now in the public sector are clumsy two piece devices which do not provide flexibility to adapt into compressed air systems and which require extensive maintenance work.